The present invention relates generally to the in vivo reaction of animal proteins with glucose, and particularly to the nonenzymatic glycosylation of proteins, and to methods for their in vivo inhibition.
The reaction between glucose and proteins has been known for some time, and in its earliest manifestation, was identified in the appearance of brown pigments during the cooking of food. This phenomenon was identified by Maillard in 1912, who observed that glucose and other reducing sugars react with amino acids to form adducts that undergo a series of dehydrations and rearrangements to form stable brown pigments. Maillard L. C. (1912) C. R. Acad. Sci., Vol. 154, pp. 66-68.
This phenomenon was found in recent years to have its parallel in vivo. Accordingly, the nonenzymatic reaction between glucose and the free amino groups on proteins to form a stable amino 1-deoxy ketosyl adduct, known as the Amadori product, has been shown to occur with hemoglobin, wherein a rearrangement of the Amadori product formed at the amino terminal of the beta chain of hemoglobin by reaction with glucose, forms the adduct known as hemoglobin A.sub.1 c. This initial reaction of the Maillard sequence was also found to occur with a variety of other body proteins, such as lens crystallins, collagen and nerve proteins. See Bunn, H. F., Haney, D. N., Gabbay, K. H. and Gallop, P. H., (1975) Blochem. Biophys. Res. Comm., Vol. 67, pp. 103-109; Koenig, R. J., Blobstein, S. H. and Cerami, A., (1977) J. Biol. Chem., Vol. 252, pp. 2992-2997; Monnier, V. M. and Cerami, A., (1983) MAILLARD REACTION IN FOOD AND NUTRITION, ed. Waller, G. A., American Chemical Society, Vol. 215, pp. 431-448; and Monnier, V. M. and Cerami, A., (1982) Clinics in Endocrinology and Metabolism, Vol. 11, pp. 431-452.
Moreover, brown pigments with spectral and fluorescent properties similar to those of late-stage Maillard products have also been observed in vivo in association with several long-lived proteins, such as lens proteins and collagen from aged individuals. An age-related linear increase in pigment was observed in human dura collagen between the ages of 20 and 90 years. See Monnier, V. M. and Cerami, A., (1981) SCIENCE, Vol. 211, pp. 491-493; Monnier, V. M. and Cerami, A., (1983) BlOCHEM. BIOPHYS. ACTA., Vol. 760, pp. 97-103; and Monnier, V. M., Kohn, R. R. and Cerami, A., "Accelerated Age-related Browning of Human Collagen in Diabetes Mellitus", (1984) PROC. NAT. ACAD. SCI., Vol. 81, pp. 583-587. Interestingly, the aging of collagen can be mimicked in vitro by the cross-linking induced by glucose; and the capture of other proteins in the formation of adducts by collagen, also noted, is theorized to occur by a cross-linking reaction, and is believed to account for the observed accumulation of albumin and antibodies in kidney basement membrane and cholesterol-bearing low density lipoprotein in the arterial wall. See, Brownlee, M., Pongor, S. and Cerami, A., (1983) J. EXP. MED., Vol. 158, pp. 1739-1744; and Kohn, R. R., Cerami, A. and Monnier, V. M., (1984) DIABETES, Vol. 33, No. 1, pp. 57-59. Cerami, A., Vlassara, H., and Brownlee, M., (1985) METABOLISM, Vol. 34, pp. 37-44.
In parent application Ser. No. 590,820 and in Pongor, S. M. et al, Supra., both incorporated herein by reference, a fluorescent chromophore was isolated and identified which was found to be present in certain browned polypeptides such as bovine serum albumin and poly-L-lysine, and was assigned a structure 2-(2-furoyl)-4(5)-2-furanyl)-1H-imidazole (hereinafter "FFI"). The compound was found to exist in a tautomeric state and has incorporated in its structure two peptide-derived amine nitrogens. The incorporation of these amine nitrogens and two glucose residues in the compound suggested that its peptide-bound precursor may be implicated in the in vivo cross-linking of proteins by glucose which is observed in the late stage of the Maillard process. See, Chang, J. C. F., Ulrich, P. D., Bucala, R., and Cerami, A., (1985) J. Biol. Chem., Vol. 260, pp. 7970-7974. This chromophore made possible the identification of the advanced glycosylation endproducts and assisted additional investigations seeking to clarify the protein aging process and if possible, to identify the specific chemistry involved to assist to develop methods and agents for its inhibition. Such method and agents were initially investigated and have been disclosed in copending application Ser. No. 798,032, the disclosure of which is incorporated herein by reference.
Further work since the development of the inhibitors in the last mentioned copending Application resulted in the identification of what appears to be an endogenous means for the in vivo elimination or removal of advanced glycosylation endproducts. This has been set forth in most recent application Ser. No. 907,747. Further development of this concept is now presented herein, and it is accordingly to this purpose that the present Application is directed.